The present invention relates to a method for forming dye images by heating, and more particularly to a method for forming excellent dye images on a dye fixing element.
A heat developable light-sensitive material is known in the field of photographic technology. Such heat developable light-sensitive materials and processes therefor are described, for example, in Shashin Kogaku no Kiso (Fundamentals of Photographic Technique), Volume of non-silver salt photography, Corona Co., Ltd., pp. 242 to 255 (1982); Eizo Joho (Image Information), April 1978, page 40, Neblette's Handbook of Photography and Reprography, 7th Ed., Van Nostrand Reinhold Company, pp. 32 to 33, U.S. Pat. Nos. 3,152,904, 3,301,678, 3,392,020, 3,457,075, British Patents 1,131,108, 1,167,777 and Research Disclosure, June 1978, pp. 9 to 15 (RD-17029).
Many methods have been proposed to form color images by heat development. In connection with a method for forming color image by bonding together an oxidized developing agent and a coupler, a p-phenylenedimaine series reducing agent and a phenol or active methylene coupler are disclosed in U.S. Pat. No. 3,531,286; a p-aminophenol series reducing agent, in U.S. Pat. No. 3,761,270; a sulfonamidophenol series reducing agent, in Belgian Patent 802,519 and Research Disclosure, Sep. 31, 1975, page 32; and a combination of a sulfonamidophenol-based reducing agent and a 4-equivalent coupler, in U.S. Pat. No. 4,021,240.
The above methods, however, have disadvantages in that since an image of reduced silver and a color image are formed at the same time in imagewise exposed areas after heat development, the color image tends to become turbid.
In order to overcome the above disadvantages, a method for removing silver images by liquid treatment and a method for transferring the dye alone to a sheet having, for example, an image receiving layer have been proposed. These methods, however, also have disadvantages in that it is not easy to separate the unreacted products and the dye, and to transfer only the dye.
In addition, the above methods have disadvantages in which a relatively long time is generally needed for development, and there is obtained only images of relatively high fog and low density.
In order to overcome the above problems, a method comprising releasing imagewise a mobile dye by heating and transferring the mobile dye to a dye fixing element containing a mordant by the use of a solvent such as water, a method comprising transferring the mobile dye to a dye fixing element by the use of a high boiling point organic solvent, a method comprising transferring the mobile dye to a dye fixing element by the use of a hydrophilic heat solvent contained in the dye fixing element, and a method in which the mobile dye is heat diffusible or sublimable and is transferred to a dye receiving element such as a support have been proposed (described e.g., in U.S. Pat. Nos. 4,463,079 4,474,867, 4,478,927, 4,507,380, 4,500,626, 4,483,914, Japanese Patent Application (OPI) Nos. 149046/83, 149047/83, 152440/84, 154445/84, 165054/84, 180548/84, 168439/84, 174832/84, 174833/84, 174834/84 and 174835/84 (the term "OPI" as used herein means a "published unexamined Japanese patent application")).
In accordance with the above methods, however, the development temperature required is still high and the processing time for obtaining dye images is not sufficiently short.
Under such circumstances, Japanese Patent Application (OPI) Nos. 218443/84 and 238056/86 have disclosed a method in which heat development is carried out in the presence of a small amount of water and a base and/or a base precursor and further a released dye is transferred, whereby acceleration of development, decreasing the developing temperature, simplifying the processing, and shortening the processing time can be realized.
In the above image forming method, a dye fixing element containing a mordant is used to fix a mobile dye.
These mordants are usually coated on a support or on other coatings by using a hydrophilic colloid such as gelatin as a binder. However, a coating containing such polymeric mordant(s) and hydrophilic colloid(s) has dynamic properties markedly different from those of a coating containing the hydrophilic colloid alone. That is, it has been found that the coating containing both the polymeric mordant and hydrophilic colloid such as gelatin is seriously decreased in tensile strength and breaking elongation as compared with a coating is brittle. Such an increase in brittleness of the coating is responsible for cracking due to thermal and dynamic strains occurring at the coating step or drying step of the coating, and imposes serious limitations on production conditions such as coating and drying.
It has also been found that the mordant layer of the dye fixing element tends to break or crack when thermal and dynamic strains are applied during the handling of the dye fixing element.
If such cracked dye fixing elements are used in the above image forming methods, unevenness is formed in development and/or in dye transfer, and a formed image appears as gaps are formed therein, and thus the image quality is seriously deteriorated.